How to texture a DEM data with satellite imagery on Blender ?
First, you need to find the satellite image that corresponds to the exact same coordinates of the DEM and is generated using same projection. 

Load the image from the satellite image in the UV/Image editor.

Go to top orthogonal view, select your model. 

Enter edit mode Tab. 

Press A to select all. Press U to UV unwrap and choose Project form view bounds.

Still in edit mode create a material that uses the image as part of the texture and set the coordinates to use the UVs.

Assign then the material to the mesh.